Most of his early years were spent in the United States, and he graduated from Georgetown University.
When Muñoz Marín returned to Puerto Rico in 1920, he rose quickly among Puerto Rican politicians, becoming a senator soon after. In Puerto Rico, he became known as a fighter for the poor people's rights and he became a fighter pro Puerto Rico's independence from the United States during the 1930s.
Muñoz Marín during World War II began a program nicknamed Operation bootstrap, designed towards helping people of Puerto Rico get better education and health, among other things. He was one of the founders of Partido Popular Democratico or PPD, which promotes Puerto Rico's commonwealth status with the United States but not a full dependence, making Puerto Rico effectively what many consider a half a nation, half a state.
In 1949, the first democratic elections were held in Puerto Rico, and Muñoz Marín was elected governor. He was once again elected in 1952, a year in which Puerto Rico officially became a commonwealth, in 1956 and 1960. In 1964, he chose not to run for another term, paving the way towards Roberto Sanchez Vilella to get selected by the PPD as Governor candidate and later , Governor. However, one of the last things he did as Governor was installing a program named Operacion Serenidad, destined towards improving the Puerto Rican's appreciation for the fine arts.
After leaving La Fortaleza, Muñoz Marín went back to being a senator.
After he died at the age of 82 in 1980, his daughter Victoria Melo Muñoz became an important politician, and in 1992, she became the first woman in Puerto Rican history to run for Governor, but she lost to Dr. Pedro Rosselló.
There is a Luis Muñoz Marín International Airport in San Juan and a Luis Muñoz Marín School in Barranquitas.